1. Field of the Invention
The present invention relates to a structure of a fuel injection nozzle attached into a cylinder head of an engine.
2. Related Art
Conventionally, in an engine such as a 2-valve type engine wherein each cylinder has one inlet valve and one exhaust valve, or a 4-valve type engine wherein each cylinder has two inlet valves and two exhaust valves, a fuel injection valve is (fuel injection valves are) inserted downward into a cylinder head. A fuel injection nozzle retainer, which may be made of a block member, axially presses the fuel injection nozzle and fixes it into the cylinder head. The fuel injection nozzle retainer is fastened at left and right ends thereof to the cylinder head by bolts.
For example, as disclosed in the Japanese Laid Open Gazette Hei. 8-121285, a holder is fastened at left and right ends thereof to a cylinder head by bolts so as to axially press a fuel injection nozzle, thereby locating and fixing it at an appointed place in the cylinder block.
Also, as disclosed in the Japanese Laid Open Gazette Hei. 9-88765, a fixture is fastened to a cylinder block by bolts so as to fix a fuel injection nozzle into the cylinder block.
A conventional engine constructed in this way is so laterally elongated (in the longish direction of its cylinder head) as to appropriate for a fuel injection nozzle retainer which is fastened at left and right ends thereof to the cylinder head 11v bolts. However, with the recent progress of miniaturization and cost saving of engines, limitation of space and cost comes to be required for mounting the fuel injection nozzle retainer,
Especially, in the case of 4-valve type engine, the fuel injection nozzle is necessarily arranged in the valve arm room because it requires to be substantially vertically inserted into the cylinder head at the substantially middle portion between inlet and exhaust valves.
In this case, the fuel injection nozzle retainer for pressing down the fuel injection nozzle is supported at one, end thereof on a vale arm shaft, thereby being arranged in the limited inner space of the valve arm room. On one side of the fuel injection nozzle retainer for each cylinder, the valve arm shaft supports the inlet valve, and on the other side, the valve arm shaft supports the exhaust valve. For example, as disclosed in Japanese Laid Open Gazette 2001-140729, a retainer is extended from the fuel injection nozzle to the valve arm shaft so as to press down and fix the fuel injection nozzle. As disclosed in this reference, while one end of the fuel injection nozzle retainer serves as a fulcrum, the other end presses down the fuel injection nozzle, and the valve arm shaft is fittingly provided thereon with inlet and exhaust valve arms on axially opposite sides thereof with respect to the retainer.
In this 4-valve type engine, shaking of the fuel injection nozzle retainer rotatably supported on the valve arm makes it difficult to locate the valve arm casing on the cylinder head, thereby spoiling facility for assembly of the valve arm casing.
Furthermore, if a cylinder boa pitch (a distance of inlet and exhaust valves) varies according to variation of engines, valve arms for inlet valves and exhaust valves must be prepared in various forms corresponding to variation of cylinder boa pitches of engines, thereby increasing costs.
A fuel pipe is inserted from outside into the valve arm room and connected top the fuel injection nozzle so as to supply the fuel injection nozzle with pressured fuel.
The fuel pipe comprises an inner pipe arranged in the valve arm room formed in the valve arm casing, and outer pipe arranged outside the valve arm casing. A pipe joint including a high-pressured seal member is screwed into a side surface of the valve arm casing so as to connect the inner pipe and the outer pipe therethrough.
While the fuel pipe comprises the inner pipe and the outer pipe connected to each other through the pipe joint, a fuel back pipe extends outward from the valve arm casing through another pipe joint screwed into a side surface of the valve arm casing. The valve arm casing is necessarily bored so as to form female screws for the respective pipe joints for conducting the, fuel pipe and the fuel back pipe, thereby increasing the number of manufacturing processes and parts.